Composition for filling the pores of grinding wheels and wheels filled therewith



Patented Mar. 13, 1951 COM-PGS'ITIONFOR FILLING THE PORES OF GRINDINGWHEELS AND WHEELS FILLED THEREWITH' Luring Coes, Jr., Brookfield, Mass,assignorto .Norton Company. Worcester, Mass-., a, corporationofJMassachusetts NoDrawingi. Application April 18, 1950, SerialfNo.156,711

" 8 Claims.

This invention relates-to. grinding wheels. and a treatment thereof toimprove their quality. This application is a continuation in part ofmycopending application serial- No. 721,665 filed J anuary 11, 1947 and.now abandoned.

One object of the inventionis. toprovide a faster cutting grinding;wheel. Another object of the invention is tozprovideatreatment which canbe. applied to' already manufactured grinding wheels to increase theefiiciency thereof. Another object of. the inventionisto provide animproved filler. for a grinding wheel. .Another object of. thinvention-late provide a rinding wheel, and, a. treatment for-a:grinding wheel which enables; it to removeea reater amount of stock foragiven amount ;of;wheelwear than heretofore,

Another object of thainventionisto: provide a filler in a grinding wheelwhich has a chemical action on metal workpieces. Another object is toprovide a filler which shall substantially reduce loading of a grindingwheel. Another ob- .lect of the invention. is to setup in v a grindingwheel a chemical action on metal chips removed from a .work piece andlodged. in aportionthereot which shall loosen such chips, thus tendingto eliminate loading. Another object isto'provide a filler for agrinding wheel" which reacts on the hot, metal chips removed from thework piece-in the grinding action so as to prevent such chips fromsticking to the wheel, thuspreventing loading in the first place.Another object is to provide a filler for a grinding wheelwhich reactson the material of the workpiece being ground to form at the grindinglinea substance which is weak, brittle, machinable" and more easilyremoved during the grinding operation. Another object is to provide afiller for a grinding wheel which remains in the pores thereof at highwheel speeds.

The invention accordingly consists in the features of construction;combinations of elements, arrangements of parts. all as will beillustratively described herein, and the scope of the application ofwhich will be indicated in the following claims.

I' provide a porousgrinding wheel'having continuous pores such as awheel bonded with any known vitrified ceramic or-resinoid bond. Such awheel may be made according toany" known method. The wheel. iscompletely formed and fired or cured orthe bond is otherwise, set priorto the treatment'now to be described, so far as the preferred form ofmy'invention is concerned.

Having formed the grindinggwheel; which may be of any desired size andshape, I make a molten composition of sulphurized fat, mineral oil and asynthetic wax. The preferred composition consists of sulphurizedf-at,10% mineral oil and 10% wax. To make the mixture I heat a quantity ofunsaturated organic natural fat (which is an ester of glycerine) andsulphur until complete reaction between the sulphur and fat takes place,thus leaving no free fat. The temperature of reaction is about C. and Iavoid temperatures which produce hydrogen sulphide. Any unsaturatednatural animal or vegetable oil fat such as linseed oil or a mixture ofsuch fats may be used as long as the total unsaturation is sufficient toallow an adequate percentage of sulphur to react withit for thepurposes'intended; Other fats which can be used are olive oil, cottonseed oil, mustard oil, stearin, butter fat, horse fat. lard, neats footoil, peanut oil, beef'tallow, castor bean oil, corn oil, mutton tallow,pumpkin seed oil.

I have found that 2.0% reactedsulphur in the oil or fat of thecomposition of, the invention is the maximum approximate percentagewhich can be economically achieved. Sulphur is the active. chemicalagent of the composition and I thus attempt to, keep the totalpercentage of sulphur as high as possible. At this stage the product ispasty andenough mineral oil is added to produce a free flowing liquid.Any desired proportion of mineral oil from 0 tov 50% of the total. oilplus fat may beused, preferably I use the minimum amount necessary toreduce the viscosity of the composition to an easily penetrating"liquid. I have found that 10% mineral oil (of the, total oil mixture) isa good percentage.

I then maintain the temperature at about 140 C. and add a wax in theproportion of 10% of the entire composition. The waxes which I can useare the diamides of ethylene diamine and carboxylic acid selected fromthe group consisting ofmyristic acid, palmitic acid and stearic acid andmixtures thereof. These acids are aliphatic straight chain carboxylicacids and are closely related to each other, having formulae as setforth in the following table.

The waxes, therefore, are the diamide of ethylene diamine and myristicacid, the diamide of ethylene diamine and palmitic acid, the diamide ofethylene diamine and stearic acid and mixtures of such .diamides. Thediamide of myristic acid has a melting point between 137 C. and 139 C.and is soluble in the sulphurized fat at about 140 C. and is thepreferred wax. The diamides of palmitic acid and of stearic acid havemelting points slightly lower than that of the diamide of myristic acid,but in each case above 120 C. All of these waxes, when molten, aresoluble in the sulphurized natural fat at temperatures of about 140 C.and above. When ethylene diamine at a temperature above 100 C., thepolymer is formed which has the following structure:

CH3 (CH2) 12CONHCH2- CH2--NHCO(CH2) 12CH3 This is the diamide ofethylene diamine and myristic acid. The other diamides of ethylenedlamine are similarly formed by reactiong ethylene diamine and the acid(palmitic or stearic). In the above reaction water is liberated. Thefunction of the wax is to gel the composition upon cooling. However Imaintain the temperature at about 140 C. until the process is completed,as follows.

Having made the composition of the invention and maintained it is amolten state, I submerge the grinding wheel in it to fill the pores ofthe wheel. The pores may be more completely filled if the compositionand wheel are placed in a closed chamber, and the air therein is firstevacuated and then readmitted while the wheel is submerged. The wheel isthen left in the composition while the composition is allowed to cool.Upon cooling, the composition forms a gel, whereupon the wheel isremoved from the composition and the excess cut off. The amount of highmelting wax used in the composition is best adjusted so that thegelatinous filling has no tendency to be thrown out of the grindingwheel when it is running at grinding speed. Since the nascent sulphur isthe efiective agent in improving the grinding action, increasing thepercentage of wax content in the composition unnecessarily reduces theeffective percentage of sulphur. The purpose of the wax is to form a gelwhich holds the filler in the grinding wheel against centrifugal force.The amount of wax should be between and of the entire composition.

The wheel may now be used for grinding. A number of grinding wheels weretreated (filled) according to the invention as just described, thespecific wax used having been the preferred wax, the diamide of ethylenediamine and myristic acid, and these wheels, when used on stainlesssteel, removed as much as 545%, nearly five and a half times, the stockremoved by an untreated wheel of the same grade and structure otherwise.The wheels of the invention had a freer cutting action and less tendencyto load. Wheel wear was reduced by as much as 55%.

The improved cutting ability of wheels containing the composition of theinvention over wheels not containing it is shown by the following table.In each case the wheels used were made of crystalline alumina abrasivegrains of grit size 80, bonded with a vitrified bond and hav ing anopen, porous structure. The wheels each had a diameter of three inches,a thickness of one half inch and a hole of seven-eighths inch diameter.The specifications for all of the wheels were the same except that thegrade of the bond in the wheels numbered 1 to 3 respectively progressedfrom soft to medium, being designated H, I, and J respectively, where Arepresents an extremely soft grade wheel and Z an extremely hard grade.Each wheel of a designated number was exactly the same except that thewheels designated Untreated contained no filler in the pores, whilethose designated Treated had been filled with the composition of andaccording to the invention. In each treated wheel the wax was thediamide ethylene diamine and myristic acid but the function of the waxis to produce the gel and the function of the gel is to keep thesulphurized natural fat in the wheels until it is actually consumed ingrinding-hence the other two waxes can be used and will give comparableresults for they too will produce gels which will keep the sulphurizednatural fat in the wheels until actually consumed in grinding. The wheelnumber 3 designated Standard treatment was treated with a composition ofbeeswax and paraffin heretofore used in treating wheels. These wheelswere tested in a grinding machine by grinding a cylindrical test bar ofstainless steel one and one half inches in diameter heldin a rotatingchuck with a total grinding wheel infeed of 20 mils at a constant ratefor all wheels tested. Units of wheel wear and metal removed are givenin mils. Metal removed was measured directly on the diameter of the workpiece in each run, and wheel wear was found by subtracting the metalremoved in each run from the total wheel feed of 20 mils in each case.

All of the above wheels which were treated with the compositionaccording to the invention were also tested on a rotating brasscylindrical test piece. None of these wheels so treated showed anymeasurable wheel wear in 20 mils total wheel feed. These tests show amarked improvement in the cutting action due to the presence of sulphurin gelatinized form.

Having thus given concrete embodiments of my invention, the same shouldnot be limited by the theories which I have as to the reasons forimproved efliciency of grinding wheels made in accordance herewith.Nevertheless for a clearer understanding of the invention I now give myviews as to the underlying cause of the improved results. Sulphur andmetals, when combined in the presence of heat form metal sulphides. Inevery efiicient grinding operation heat is generated at the grindingline or point of contact where the wheel grinds the work. The heatgenerated decomposes the sulphurized fat composition of the invention inthe grinding wheel pores and frees the sulphur which recombines with themetal -being ground to form a sulphide answer of that metal.'Such'metalsulphides are weak, brittle and. easily :machinablen andarethusrmore easily ground away by the wheel. QThgsiilDhides have a much;lowenmelting point than; the pure metal and the grinding heat convertsthem more easily into the soft red hot particles which are seen as ashower of" sparks in a drygrinding operation. Everygrinding-wheel has atendency to load to some; extentpthat is to accumulate particles of thematerial being. ground. Loading may involve an actual depositofmaterialfrom the work piece into'the pores of the grinding wheel or asticking of the material of the work piece to the abrasive grains or tothe bond or a combination of these. The hot particles which are tornaway from the work piece by the grinding wheel have a tendency to weldthemselves to the wheel. However the production of a chemical reactionon the metal particles by sulphur in the presence of heat to form ametal sulphide reduces the adhesion of the particles to the wheel andtends to prevent loading. If any pure metal has already stuck to thewheel, a chemical reaction involving it will tend to loosen it so thatit will fly off the wheel. The composition of the invention forms a gelupon cooling which is resilient and deformable under stress yet does notflow as does parafiin or other solid waxes or fats under continuedpressure or stress. The gel is made strong enough to resist the stressesat grinding speeds and so it tends always to return to its originalposition and shape in the pores of the wheel. Just enough nascentsulphur is then freed by the heat of grinding to form the metalsulphides with no loss of sulphur so that the beneficial efiect of thecomposition of the invention upon the grinding operation is continuousand long lasting.

The nascent sulphur liberated by the decomposition of the sulphurizedfat is much more effective in forming sulphides of the material removedas an aid to grinding than sulphur as such would be.

The amides gel holds itself and the total composition in the pores ofthe wheel as explained. The sulphurized fat and the mineral oil aredissolved in the gel. The mineral oil and the sulphurized fat. whenmelted by the grinding action, act as lubricants and so promotegrinding. The sulphurized fat is sufficiently lubricating so that themineral oil could be omitted. Its function is chiefly to reduceviscosity at any given temperature, so the temperature of thecomposition when the wheel is impregnated therewith, can be lower if themineral oil is included than if it were omitted. Thus the mineral oilfacilitate impregnation. The total composition, with or without themineral oil, is still a gel. This gel, at room temperature, is fairlystiff, about as stiff as paraffin.

It will thus be seen that there has been pro-- vided by this inventionan article and a composition in which the various objects hereinaboveset forth together with many thoroughly practical advantages aresuccessfully achieved.

As many possible embodiments may be made of the above invention and asmany changes might be made in the embodiments above set forth, it is tobe understood that all matter hereinbefore set forth is to beinterpreted as illustrative and not in a limiting sense.

I claim:

1. A grinding wheel comprising abrasive grains, bond holding the grainstogether to form the wheel, there being pores in the wheel, and a geltil which is the-diamide or ethylenezdiamine and carboxylic acidselectedfrom the group. consisting of myristic acid, palmitic acid andstearic acid and mixtures thereof having in solution therein asulphurized natural fat, said diamide being from 5% to 20% of theentirecomposition, thesulphurized fat having from 10% to 20% sulphur-and thebalance of the composition over-the diamide beingat least 50% saidsulphurized fat, saidgel filling someofthe pores of the-wheel.

2. A grinding-wheel comprising abrasive grains, bond holding the grainstogether to form the wheel, there being pores in the wheel, anda gelwhich is the diamid of ethylene diamine and carboxyli'o-acid selectedfrom the group consisting of myristic acid, palmitic acid and stearicacid and mixtures thereof having in solution therein a sulphurizednatural fat and mineral oil, said diamide being from 5% to 20% of theentire composition, the sulphurized fat having from 10% to 20% sulphurand the balance of thecomposition over the diamide being at least 50%said sulphurized fat, said gel filling some of the pores of the wheel,said mineral oil being not more than 50% of the total oil plus fat.

3. A grinding wheel comprising abrasive grains, bond holding the grainstogether to form the wheel, there being pores in the wheel, and a gelwhich is the diamid of ethylene diamine and myristic acid having insolution therein a sulphurized natural fat, said diamide being from to20% of the entire composition, the sulphurized fat having from 10% to20% sulphur and the balance of the composition over the diamide being atleast 50% said sulphurized fat, said gel filling some of the pores ofthe wheel.

4. A grinding wheel comprising abrasive grains, bond holding the grainstogether to form the wheel, there being pores in the wheel, and a gelwhich is the diamide of ethylene diamine and myristic acid having insolution therein a sulphurized natural fat and mineral oil, said diamidebeing from 5% to 20% of the entire composition, the sulphurized fathaving from 10% to 20% sulphur and the balance of the composition overthe diamide being at least 50% of said sulphurized fat, said gel fillingsome of the pores of the wheel, said mineral oil being not more than 50%of the total oil plus fat.

5. As a new composition of matter, a gel which is the diamide ofethylene diamine and carboxylic acid selected from the group consistingof myristic acid, palmitic acid and stearic acid and mixtures thereofhaving in solution therein a sulphurized natural fat, said diamide beingfrom 5% to 20% of the entire composition, the sulphurized fat havingfrom 10% to 20% sulphur and the balance of the composition over thediamide being at least 50% said sulphurized fat.

6. As a new composition of matter, a gel which is the diamide ofethylene diamine and carboxylic acid selected from the group consistingof myristic acid, palmitic acid and stearic acid and mixtures thereof,having in solution therein a sulphurized natural fat and mineral oil,said diamide being from 5% to 20% of the entire composition, thesulphurized fat having from 10% to 20% sulphur, and the compositionapart from the diamide being at least 50% said sulphurized fat, saidmineral oil being not more than 50% of the total oil plus fat.

7. As a new composition of matter, a gel which is the diamide ofethylene diamine and myristic acid having in solution therein asulphurized natural fat, said diamide being from 5% to 20% 7 of theentire composition, the sulphurized fat having from 10% to 20% sulphurand the balance of the composition over the diamide being at least 50%said sulphurized fat.

8. As a new composition of matter, a gel which is the diamide ofethylene diamine and myristic acid having in solution therein asulphurizednatural fat and mineral oil, said diamide being from 5% to20% of the entire composition, the sulphurized fat having from 10% to20% sulphur and the composition apart from the diamid being at least 50%said sulphurized fat, said mineral oil being not more than 50% of thetotal oil plus fat.

LORING COES, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,240,302 Jones Apr. 29, 19412,425,392 Robinson et a1 Aug. 12, 1947 FOREIGN PATENTS Number CountryDate 321,240 Great Britain Nov. 7, 1929

1. A GRINDING WHEEL COMPRISING ABRASIVE GRAINS, BOND HOLDING THE GRAINSTOGETHER TO FORM THE WHEEL, THERE BEING PORES IN THE WHEEL, AND A GELWHICH IS THE DIAMIDE OF ETHYLENE DIAMINE AND CARBOXYLIC ACID SELECTEDFROM THE GROUP CONSISTING OF MYRISTIC ACID, PALMITIC ACID AND STEARICACID AND MIXTURES THEREOF HAVING IN SOLUTION THEREIN A SULPHURIZEDNATURAL FAT, SAID DIAMIDE BEING FROM 5% TO 20% OF THE ENTIRECOMPOSITION, THE SULPHURIZED FAT HAVING FROM 10% TO 20% SULPHUR AND THEBALANCE OF THE COMPOSITION OVER THE DIAMIDE BEING AT LEAST 50% SAIDSULPHURIZED FAT, SAID GEL FILLING SOME OF THE PORES OF THE WHEEL.